The invention relates in general to an apparatus used for the thermochemical scarfing of metal workpieces. More particularly, the invention relates to an improved lower pre-heat block assembly for use with such an apparatus in which the block assembly is constructed and arranged to create a sheet-like gas flow for shielding a separate sheet-like oxidizing gas flow generated during the scarfing process to attain a smooth scarfed surface on the metal workpieces.
In the production and finishing of metal workpieces, for example elongate steel slabs, billets, and bar stock, the steel is conditioned or surface finished by creating relative motion between the steel workpiece and a scarfing apparatus having at least one scarfing unit positioned along the top, bottom, or side surfaces of the workpiece to eliminate surface defects such as cracks, seams, slag inclusions, surface oxides, and mechanical defects resulting from the rolling or casting process, for example. One known type of such a scarfing apparatus includes top, bottom, and opposed side scarfing units that are mounted across the width and end portions of the workpiece to concurrently scarf each of the sides of the workpiece as it is passed through the scarfing apparatus and between the scarfing units so provided.
The top, side, and bottom scarfing units of the scarfing apparatus each include a manifold and head assembly constructed and arranged to receive and distribute both oxygen and fuel gas to opposed upper and lower pre-heat blocks or block assemblies provided as a part of each such scarfing unit. The respective upper and lower pre-heat blocks are spaced from one another to define an oxygen scarfing slot therebetween, and through which a quantity of oxygen is passed under pressure and directed toward the workpiece to enable the thermochemical scarfing process to occur. The lower pre-heat block will typically include a fuel gas channel having a discharge opening positioned adjacent the oxygen slot formed by the upper and lower pre-heat blocks for discharging a fuel gas adjacent the oxygen flow for the purpose of maintaining the oxidation reaction on the surface of the workpiece, and for also shielding the oxygen flow from aspiration, i.e., from mixing with ambient air, which tends to diminish the effectiveness of the thermochemical scarfing process.
One example of such a known type of lower pre-heat block is disclosed in U.S. Pat. No. 2,838,431 to Allmang et al., in which the pre-heat block is disclosed as being of one piece construction and includes a spaced series of fuel gas outlets extending across the width of the front face of the block. The fuel gas is delivered to the inlet ports through a number of laterally spaced fuel gas lines which extend from a rear face of the block to a transverse internal bore positioned just behind, and in communication with the inner ends of the outlet ports. An elongate dividing rod, or bar, comprising a number of spaced transverse discs is positioned within the bore so as to divide the bore into a series of uniform gas distribution chambers. The ends of the bore are closed with end seals in known fashion.
Although the fuel gas outlet ports defined in the front face of the lower pre-heat block of Allmang, et al. were an improvement over the then-known scarfing machines, in that the fuel gas ports were closely spaced with respect to one another in the effort to prevent outside air from aspirating with the oxidizing gas stream, the problem still remained that outside air would tend to be drawn toward and between the fuel gas outlet ports such that outside air would aspirate with the oxidizing gas flow.
As known to those of skill in the art, the shielding of the sheet-like oxygen stream, or oxidizing gas flow created when oxygen is passed between the upper and lower pre-heat blocks is most critical in producing a smooth scarfed surface on the workpiece being scarfed as any variation or inconsistency in the lower pre-heat block fuel gas flame can cause a variation in the scarfed surface. Any such variation can lead to non-uniform metal removal, with ridges and valleys being the result, such that the scarfing depth must be increased in order that these ridges or valleys be removed, i.e., a sufficient quantity of the surface of the object must be removed to provide for the removal of all such surface defects which pre-existed the scarfing process, as well as those which may have been caused by the scarfing process. As a result, the scarfing apparatus of Allmang, et al. and others similarly constructed, led to the removal of excess metal, causing otherwise satisfactory metal to be removed which increases yield loss rates during the workpiece finishing process.
The scarfing apparatus of Allmang et al. was improved upon in U.S. Pat. No. 3,231,431 to Allmang by adding an elongate baffle strip of an approximate one-half (xc2xd) inch length positioned approximately one-quarter (xc2xc) inch below the oxygen slot to prevent the aspiration of ambient air into the oxygen stream, as disclosed in Column 2, Lines 34-72, and Column 3, Lines 1-13 thereof. As stated in Column 2, Lines 61-65 of Allmang, it was believed that a confining action caused by the baffle strips on both sides of the oxygen-fuel mixture prevented atmospheric air from aspirating with the oxygen at a point adjacent to each row of pre-heat (gas outlet) ports.
Although the patent to Allmang represented an improvement in the art, the need still existed for an improved scarfing apparatus which would more consistently produce a smooth surfaced scarfed metal workpiece. It was to the attainment of this object that the lower pre-heat block assembly of Showalter, et al. disclosed in U.S. Pat. No. 5,497,976 was developed. Showalter attained a smooth surface scarf by providing a lower pre-heat block assembly for use in a thermochemical scarfing apparatus which included an improved fuel gas delivery system for delivering a stream of fuel gas uniformly across the full width of the metal workpiece, and which shielded the oxidizing gas flow to ensure that the peaks and valleys resulting from the use of the earlier known scarfing devices were minimized. This was accomplished by providing a two-piece lower pre-heat block assembly having a base member or block, and an extension releasedly fastened thereto in engaging and overlying relationship on the front face of the block. An elongate gas discharge slot was machined into the extension, which slot communicated with a spaced series of gas discharge ports defined within and extending longitudinally across the front face of the block. The extension also included internal baffles for inducing turbulence in the fuel gas flow to ensure complete mixing of the fuel gas, such that the fuel gas would be emitted through the gas discharge slot as a uniform flow across the face of the extension.
The lower pre-heat block assembly of Showalter et al. represented a significant advance in the art, but it required that a two-piece lower pre-heat block assembly be manufactured in which a precisely machined slot is required within the extension, and which also required the use of internal baffles for inducing turbulence in the fuel gas flow to ensure that the fuel gas is distributed uniformly across the width of the extension in order to prevent ambient air from aspirating with the oxidizing/oxygen gas flow as it is passed between the upper and lower pre-heat block assemblies, and directed toward the metal object or workpiece to be thermochemically scarfed.
What is needed, therefore, but seemingly unavailable in the art is an improved lower pre-heat block assembly for use with a thermochemical scarfing apparatus which is simple in design and manufacture, and which will ensure that a sheet-like fuel gas flow is produced for shielding the oxidizing gas flow.
In the lower pre-heat block assembly of Showalter et al., the disclosed gas discharge slot is provided within an otherwise conventional extension having a baffle similar to that disclosed in U.S. Pat. No. 3,231,431 to Allmang, such that should the fuel gas discharge slot became plugged or obstructed at any point along its length, the probability exists that ambient air will be allowed to aspirate with the oxidizing gas flow, which may lead to the formation of peaks and valleys during the metal scarfing process. What is needed, therefore, is an improved lower pre-heat block assembly for use with a scarfing apparatus in which a gas discharge outlet which is less likely to become obstructed is defined within the modular base or block, and with which the extension can be placed in engaging and overlying position such that it defines a gas discharge orifice of a desired size in the face of the block for simplifying the manufacture of the lower pre-heat block assembly, and for allowing the fuel gas to be distributed evenly across the width of the lower block assembly so that the lower block will perform satisfactorily even if there may be plugs or obstructions in the gas discharge outlets to shield the oxidizing gas flow from ambient air during the scarfing process.
Lastly, although the baffle of the patent to Allmang proved useful in minimizing the aspiration of ambient air within the oxidizing gas flow, this problem still persists, even with the improved lower pre-heat block assembly of Showalter et al. Accordingly, what is needed is an improved lower pre-heat block assembly for use with a thermochemical scarfing apparatus which is constructed to utilize the oxidizing gas flow as it is passed over the lower pre-heat block assembly to pneumatically compress, or squeeze, the fuel gas between the oxidizing gas flow and the lower pre-heat block assembly such that the fuel gas is uniformly distributed across the width of the lower pre-heat block assembly, and for forming a sheet-like fuel gas flow which shields and adjoins the oxidizing gas flow as it is continues on toward the metal workpiece to be scarfed so as to minimize the likelihood that peaks and valleys will be formed during the scarfing process, and to improve production yields during the metal finishing process.
The present invention provides an improved lower pre-heat block assembly for use with a thermochemical scarfing machine which overcomes some of the design deficiencies of the other lower pre-heat block assemblies known in the art. The lower pre-heat block assembly of this invention provides a simple, efficient, and highly flexible apparatus for uniformly distributing a fuel gas across the width of a lower pre-heat block assembly, and for forming the fuel gas into a sheet-like fuel gas flow which adjoins and shields an oxidizing gas flow passed over the lower pre-heat block assembly and along a flow path leading toward a metal object, or workpiece, to be thermochemically scarfed during the steel finishing process. The relative simplicity of this improved lower block assembly in comparison with the known lower block assemblies allows for a greater degree of reliability in shielding the oxidizing gas flow, and in maintaining its sheet-like flow characteristics along the flow path to minimize the formation of peaks and valleys in the surface of the metal workpieces being thermochemically scarfed with the scarfing apparatus.
The term xe2x80x9csheet-likexe2x80x9d as used herein means a flow which is in the form of a sheet.
This invention attains this high degree of flexibility, maintainability, reliability, as well as simplicity in design and operation, by providing a lower pre-heat block assembly for use with the thermochemical scarfing apparatus comprising a modular block having opposed upper and lower faces, opposed end faces, and opposed front and rear faces extending between the end of faces in a longitudinal direction. A gas discharge outlet is defined within, and extends longitudinally across the front face of the block. A modular extension is engaged on, and partially overlies the front face of the block. The extension may partially overlie the gas discharge outlet to define a gas discharge orifice in communication with the gas discharge outlet on the front face of the block, as desired. The extension is constructed and arranged to be releasably secured to the front face of the block. A feature of this construction is that the lower pre-heat block assembly of this invention does not therefore require the fabrication of a precisely machined fuel gas discharge slot or orifice therein and is less susceptible to dirt or other obstructions fouling the gas discharge outlet, which may in turn prevent the distribution of the fuel gas uniformly across the lower block assembly. This therefore minimizes the likelihood of disruptions in the oxidizing gas flow, and allows for a lower pre-heat block assembly which is simple to manufacture, and provides greater production efficiencies when in use.
The extension has a separate upper face and an opposed lower face, opposed end faces, and opposed front and rear faces extending between the end faces in a longitudinal direction. The rear face of the extension is placed in an overlying relationship on the front face of the block. The upper face of the extension is recessed with respect to, i.e. it is positioned below, the level of the upper face of the block such that the extension is stepped down a pre-determined height from the upper face of the block. The extension further comprises a leading edge spaced from the front face of the block which extends longitudinally along the length of the extension. The leading edge of the extension may be recessed with respect to the front face of the extension for forming a notch to protect, or shield, the leading edge with the front face of the extension.
The lower pre-heat block assembly of this invention is intended for use in a conventional thermochemical scarfing apparatus in which an upper pre-heat block assembly is provided, the lower pre-heat block assembly being spaced from and opposed to the upper block assembly such that an oxygen slot is defined by and between the two block assemblies, and through which oxygen is passed and formed into an oxidizing gas flow moving along a flow path extending toward the metal workpiece to be scarfed. In fashion heretofore unknown in the art, the unique construction of the lower pre-heat block assembly of this invention makes use of the expansion of the oxidizing gas flow to xe2x80x9cpneumaticallyxe2x80x9d compress or squeeze the fuel gas between the oxidizing gas flow, the front face of the modular block, and the second upper face provided on the extension along the longitudinal length of the lower pre-heat block assembly, i.e., across the width of the workpiece being scarfed, to ensure that the fuel gas is uniformly distributed along substantially the full longitudinal extent of the front face of the lower pre-heat block assembly, and to pass the compressed and now distributed fuel gas as a substantially uniform and sheet-like gas flow through a pneumatic slot formed by and between the oxidizing gas flow and the leading edge of the extension to ensure that the sheet-like fuel gas flow underlies and adjoins the sheet-like oxidizing gas flow as they then both flow together along the flow path toward the metal workpiece to be scarfed. The unique construction of this lower pre-heat block assembly thus provides for the uniform distribution of fuel gas across the width of the oxidizing gas flow to greatly minimize the likelihood of ambient air aspirating with the oxidizing gas flow, and is constructed to keep a smooth sheet-like oxidizing gas flow moving toward the workpiece so that a more smoothly scarfed surface of the workpiece results, thus resulting in greater production yields and manufacturing efficiencies than the known scarfing devices.
The improved lower pre-heat block assembly of this invention, therefore, also results in a new method of shielding the oxidizing gas flow of a thermochemical scarfing machine during use, which method comprises the steps of passing the sheet-like oxidizing gas flow over the upper surface of the modular base or block of the lower pre-heat block assembly; discharging a fuel gas from a fuel gas discharge outlet defined in the front face of the block adjoining a first upper face thereof so as to form a sheet-like fuel gas flow which underlies the oxidizing gas flow; compressing the sheet-like fuel gas flow between the front face and a second upper face formed on the extension of the lower pre-heat block assembly with the oxidizing gas flow so that the sheet-like fuel gas flow is substantially and uniformly distributed under the sheet-like oxidizing gas flow, whereupon both of the sheet-like gas flows pass together along the flow path toward the workpiece to be scarfed, the sheet-like gas flow shielding the sheet-like oxidizing gas flow from ambient air to permit the scarfing of a smooth surface on the metal workpiece without the peaks and valleys caused by ambient air being allowed to aspirate with the oxidizing gas flow.
The step of forming the fuel gas into the sheet-like fuel gas flow also includes the step of pneumatically squeezing the fuel gas against the front face of the block, the upper face of the extension, and the oxidizing gas flow, and passing the fuel gas through a pneumatic slot defined by the oxidizing gas flow and a leading edge extending the longitudinal length of the upper face of the extension to form the fuel gas into the sheet-like fuel gas flow adjoining the oxidizing gas flow.
It is, therefore, an object of the present invention to provide an improved lower pre-heat block assembly for use in a metal scarfing apparatus which will reliably and consistently produce a smooth scarfed surface on a metal workpiece being thermochemically scarfed therewith.
It is another object of the present invention to provide an improved lower pre-heat block assembly for use in a metal scarfing apparatus which is simple in design and construction, is rugged and durable in use, and is easy to use and maintain.
Yet another object of the present invention is to provide an improved lower pre-heat block assembly for use in a metal scarfing apparatus which will minimize the likelihood of ambient air aspirating with the oxidizing gas flow, and for forming a sheet-like fuel gas flow adjoining the oxidizing gas flow to shield the oxidizing gas flow during the thermochemical scarfing process.
It is to these objects, as well as the other objects, features, and advantages of the present invention, which will become apparent upon reading the specification, when taken in conjunction with the accompanying drawings, to which the invention is directed.